I. Field of the Invention
This invention pertains to a hand-piece for an injection device or similar apparatus used to inject a therapeutic fluid into human or animal tissues, and more particularly to a hand-piece which includes a needle movable along a longitudinal axis, which needle is optionally rotating about said axis as well.
II. Description of the Prior Art
It is well documented in both dental and medical literature that pain, tissue damage and post-op complications have long been tolerated as negative side effects from the use of existing hypodermic drug delivery injection systems. The pain and tissue damage are as a direct result of uncontrolled flow rate in conjunction with excessive pressures created during the administration of drug solutions within the tissues. Subjective pain response of a patient has been demonstrated to be minimized at specific flow rates during the administration of a drug. Also, it has been scientifically demonstrated that particular pressures (excessive without occlusion, per se) for a specific tissue type will cause damage. It is therefore critical that a specific flow rate in conjunction with a specified pressure range be maintained during the delivery of fluids (drugs) when a subcutaneous injection is given preventing subjective pain response as well as tissue damage. It is also necessary that this system have the capability to aspirate under controlled conditions of rate and pressure to avoid the same negative side effects during fluid movement. U.S. Pat. No. 5,180,371 to Spinello, incorporated herein by reference, presented an invention which allowed a rate to be set for the drug via a hypodermic needle disposed in a hand-piece.
One of the goals of dentistry and medicine should be to administer care to patients in the most humane and painless manner. The sine qua non of any treatment is to produce a desired result without causing damage or pain to the individual. Therefore there is an important need in all fields of surgery for an injection system which can be used to administer a fluid while causing substantially no pain or tissue damage to the patient.
Another goal of dentistry and medicine in general is to insure that during any procedure involving interaction between a dentist or other care giver and a patient, utmost care is taken to protect the care giver from injury and/or infection with diseases.
The use of hollow-core needles is the standard in drug delivery in medicine and dentistry. The use of the hollow-core needle dates back over 150 years when Charles Pravaz, a French general surgeon, patented such a device. It has been recognized that the use of hypodermic needles, which activity is endemic in the field, is one particularly hazardous activity which could cause injury. More particularly, the use of a hypodermic needle in dentistry and other medical fields has been shown to put the operator at risk to inadvertent needle sticks presenting a potential high risk to infection disease transmission for health care workers.
Currently, there are several auto-retraction type syringes are known that provide increased safety by allowing the protruding needle to be retracted into a protective sheath after use. However, current syringes require the use of a palm-thumb grasp during their use. This type of hand dexterity presents a potential risk of inadvertent needle stick during entry and withdrawal from the patient tissues. Other syringes are provided with removable caps. However, this configuration does not solve the problem in a satisfactory manner.
All of these prior art references have either one or more of the following deficiencies.                1) The use of a hollow needle that is rigidly affixed to the end of a syringe-, tubing or hand-piece. The protruding needle presents a risk of inadvertent needle stick to the operator.        2) Existing auto-retracting syringes and the like require the operator to use a palm-thumb grasp to operate. This structure creates an increased risk of inadvertent needle stick to the operator.        3) Existing auto-retracting syringes and the like require the operator to make use of the hand to physically retract the needle, thereby, making it difficult and cumbersome to perform.        
Some prior art syringes and needles with sheaths or caps are disclosed in the following U.S. Pat. Nos.: 5,120,310; 5,188,613; 5,267,961; 5,389,076; 5,423,758; 5,578,011; 5,632,733; 5,637,092; 5,810,775; 5,030,209; 4,911,693; 4,900,310; 4,813,426; 4,795,432; 4,664,654; 4,695,274; 4,966,592; 4,747,831; 4,900,311; 5,411,487; 5,106,379; 5,713,873.
With the rise of infectious diseases, i.e., hepatitis and AIDS, protection of the health care workers has become a needed priority because, as indicated in the medical/dental literature, inadvertent needle sticks represent a significant risk to our health care providers. In the past 15 years regulatory agencies such as OSHA have attempted to improve the use and safety of needles in the health care industry further accentuating the need for an effective means of preventing needle sticks.
In addition, various medical organizations have suggested and several states have instituted rules for the protection of care givers while providing injections to patients. More specifically, rules have been promulgated requiring that injection needles on syringes be provided which can be easily removed prior to an injection and re-installed immediately after an injection.
The proposed invention has been designed to eliminate the potential of inadvertent needle sticks during and after use.
Another related problem addressed by the present invention pertains to the deflection or bending of needles as they are inserted into the tissues of a patient. This deflection occurs because the needle is usually flexible because of its relatively small cross-sectional area and cannot resist effectively the axial and radial forces present during the insertion. The deflection is undesirable because it provides additional resistance during the insertion, to the movement of the needle and makes it difficult to guide the needle to a particular site. Moreover, if a needle is deflected, bent or otherwise deformed during insertion, it may cause more pain to the patient, trauma to the local tissues and other undesirable effect. It has been discovered (as disclosed in co-pending provisional application serial No. 60/173,374 filed Dec. 28, 1999), incorporated herein by reference, that these disadvantages are eliminated or at least alleviated if the needle is rotated about its longitudinal axis as it is advanced along the axis into the patient tissues. While rotating devices are known which rotate about their longitudinal axes to allow drilling through bony tissues, these devices do not allow high level tactile control during use. Other syringes do not allow the use of a bi-directional rotational insertion technique to be used during a power assisted injection process.